In a variety of engineering applications, clamping or containment devices are used for exerting an inwardly radial pressure upon a generally cylindrical object or body. For example, sleeve-like clamping devices are used, especially in petroleum and gas transmission applications, to make butt joints between adjoining sections of a pipeline where conventional welding techniques cannot conveniently or economically be employed. Similarly, clamping devices are used to effect emergency repairs on pipeline ruptures. In a somewhat different sort of application, it is sometimes necessary to contain a highly pressurized fluid or gas, produced by, say, an explosion, in a cylindrical chamber which must, nevertheless, be capable of being opened for access to the interior thereof. An example of such a device might be the hydrostatic pipe splicing apparatus disclosed in U.S. Pat. No. 4,330,918.
One well known clamping device for the above purposes is the split-sleeve, exemplary versions of which are shown in Prior Art FIG. 1. As can be seen, this type of device generally comprises a cylindrical or sleeve-like body which is longitudinally split into two mating halves 1 and 2 which are adapted to be joined together by bolts 3 in a clamping relationship.
It has long been recognized that, despite its utility, the split-sleeve clamp possesses a number of limitations and disadvantages. For one thing, it is a time consuming matter to tighten the many bolts of a split-sleeve clamp, a distinct disadvantage when the clamp is being used in a hostile environment, for example, when it is being applied by divers to an underwater pipeline. Further, if the clamp is to be subjected to any considerable amount of stress, it is critical that the bolts be equally torqued in order to avoid localization of stress and the ensuing phenomenon whereby the bolts, one-by-one, "unzip". In a preferred version of this device, shown in exemplary fashion in FIG. 1, the bolts pass through the so-called "average stress line" of a thick walled cylinder of the clamping body so that the clamp is able to maintain circularity under stress. Doing this, however, brings the bolt holes extremely close to the inside bore of the clamping device and, under high internal pressure, the weakened bore wall may rupture. Still another structural defect resides in the fact that the bolts used to fasten the clamping device halves together must be spaced fairly widely apart in order to leave room for their heads or nuts 4. This means that the total cross sectional area of the bolts is relatively small in comparison to the bearing surface area which they require. Accordingly, there is an inherent limitation in the strength of a split-sleeve clamp which is held together using bolts, and devices of this type simply cannot be used in certain extreme applications.
In view of the above mentioned drawbacks of bolted split-sleeve clamping and containment devices, it is the general object of the present invention to provide an improved clamping or containment device which is substantially free of these limitations.
It is a more particular object to provide a clamping or containment device which is able to exert clamping forces far in excess of those practically achievable with bolted split sleeve devices of equivalent size and weight.
Another object is to provide a clamping or containment device which is able to maintain circularity by the direction of clamping force through the device average stress line, and which yet possesses a bore wall of acceptable thickness.
Still another object is the provision of a clamping or containment device which does not utilize a plurality of bolts which must be uniformly tightened and which, accordingly, may be used more rapidly and easily than existing devices relying on bolts.
As still further objects, it is the intent of the present invention to provide a novel clamping apparatus which may be applied to a number of tasks in various environments. Thus, it is a particular object of the invention to provide a clamping device to clamp butted splice sections of a pipeline or to patch ruptures in a pipeline. Another particular object is to provide an improved high pressue containment vessel which is suitable for use in the practice of the general hydrostatic pipe splicing method taught by U.S. Pat. No. 4,327,471.